Some internal combustion engines include engine control systems that deactivate cylinders under low load situations. This may be referred to as variable displacement. For example, an eight-cylinder engine may be operated using only four cylinders. It may be possible to obtain increased fuel efficiency if an engine can be operated on less than the full complement of cylinders during certain running conditions.
Hybrid powertrains may include an engine, an electric motor, and an electric generator. The engine may occasionally be shut down and traction provided by the electric motor or electric generator.